Elevational plant species richness patterns and their drivers across non-endemics, endemics and growth forms in the Eastern Himalaya
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Despite decades of research, ecologists continue to debate how spatial patterns of species richness arise across elevational gradients on the Earth. The equivocal results of these studies could emanate from variations in study design, sampling effort and data analysis. In this study, we demonstrate that the richness patterns of 2,781 (2,197 non-endemic and 584 endemic) angiosperm species along an elevational gradient of 300–5,300 m in the Eastern Himalaya are hump-shaped, spatial scale of extent (the proportion of elevational gradient studied) dependent and growth form specific. Endemics peaked at higher elevations than non-endemics across all growth forms (trees, shrubs, climbers, and herbs). Richness patterns were influenced by the proportional representation of the largest physiognomic group (herbs). We show that with increasing spatial scale of extent, the richness patterns change from a monotonic to a hump-shaped pattern and richness maxima shift toward higher elevations across all growth forms. Our investigations revealed that the combination of ambient energy (air temperature, solar radiation, and potential evapo-transpiration) and water availability (soil water content and precipitation) were the main drivers of elevational plant species richness patterns in the Himalaya. This study highlights the importance of factoring in endemism, growth forms, and spatial scale when investigating elevational gradients of plant species distributions and advances our understanding of how macroecological patterns arise.
KeywordsElevational gradient Endemic Growth forms Himalaya Macroecology Richness patterns
KM acknowledges the support of Department of Science and Technology INSPIRE Research Fellowship, Government of India (Grant No: DST/INSPIRE Fellowship/2012/432). The financial support to MKP provided by the Ministry of Environment, Forests and Wildlife, Government of India and NHPC India vide grant No. J.12011/11/99-IA.I. and DU-DST-PURSE Grant is gratefully acknowledged. LPK was supported by the Australian Research Council. We also thank D. Dawa and R. Mehta for assistance.
Compliance with ethical standards
Human and animal rights
No formal approval is required for this study since this article does not contain any studies with human participants or animals performed by any of the authors.
Conflict of interest
The authors declare that they have no conflict of interest.
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